Stomach wall. Coloured Scanning Electron Micrograph (SEM) of the surface of the fundus region of the human stomach. At centre is a dark opening known as a gastric pit. Under this is the location of the secretory glands that produce digestive enzymes and acids which break down food. Around the gastric pit are a layer of epithelial cells. These cells produce a thick layer of mucus (not seen here) which lines and protects the wall of the stomach from self-digestion. The fundus is the uppermost section of the stomach which, together with the body of the stomach, contains such gastric glands. Magnification: x 1090 at 5x7cm size.